java - Implementing multiple interfaces having same method

Question

This code works perfectly. The method test() works for both interfaces. What is exactly going on under the hood? And how is this feature useful in practical scenario?

interface A
{
    void test();
}

interface B 
{
    void test();
}

class C implements A, B
{

    public void test() 
    {
        System.out.println("abc");
    }
}

   A a = new C();
   a.test();
   B b = new C();
   b.test();

Answer 1

Because it's an interface there is no harm done. You're basically using a blueprint for your C class by implementing A and B. Both A and B say that C should implement a method called test()

Your C class implements that method, so the interfaces have done their job.

It's basically your C class saying: "Oh hey, I need to implement test() because of interface A" and you implement it. Then your C class says "Oh hey, I need to implement test() again because of interface B" and it sees that there is already a method called test() implemented so it's satisfied.

You can also find more information here: JLS §8.4.8.4